mail/mutt: New hcache options change default to lmdb

• Add three new(ish) hcache options HCACHE_{LMDB,GDBM,QDBM}
• Update HCACHE_BDB to use database/db18
• Due to bdb5's EOL change the default hcache to HCACHE_LMDB. Favoring lmbd since it's performance is on par with BDB and that db18's AGPL3 licensing seems to be a point of contention.

PR: 263211